Electrical voltage testers are well known, widely available, for example, in hardware stores, and in widespread usage by not only electricians but also the general public. A common usage of such testers is to test a wall outlet to see if the normal 110-120 volts exists across the two main nodes of the outlet. The tester may also be used to test for other voltages if it is so adapted, such as whether 240 volts is present at a 240 volt outlet, also commonly found in household and industrial buildings. The tester may also be used to determine voltages between any two points, at least voltages exceeding the voltage at which the indicator illuminates, which may be between a wire thought to be hot and ground, or any other two points between which a voltage is suspected.
These voltage indicators are typically used for a quick check to determine if a voltage is present. They are relatively inexpensive items, and because of their widespread usage they must be easy and convenient to use.
U.S. Pat. No. 4,259,635 discloses a combined continuity and voltage tester having a pair of probes spaced for insertion into an electrical wall socket. One of the probes is permanently affixed to the housing of the tester. The other probe is connected by a lead wire to the housing and can be removably attached to the housing so that it is parallel to and spaced from the other permanently connected probe so as to fit in a wall socket. The advantage of this tester is that wall sockets can be tested with one handed operation. The problem, however, is that only one of the probes has a lead wire attached to it and the other probe is permanently affixed to the housing, making the permanently affixed probe rather clumsy to handle when probing electrical nodes other than the nodes of a wall socket.